Apparatus for driving drum of washing machine

ABSTRACT

A radial core type double rotor brushless direct-current motor is provided in which a double rotor structure is employed with inner and outer rotors which are doubly disposed and thus a stator core is completely divided. The motor includes a rotational shaft which is rotatably mounted on a housing of an apparatus, cylindrical inner and outer yokes which are rotatably mounted on the center of the housing, inner and outer rotors including a number of magnets which are mounted with the opposing polarities on the outer surface of the inner yoke and the inner surface of the outer yoke, and a number of cores assemblies which are installed between the inner and outer rotors in which a number of coils are wound around a number of division type cores, respectively.

RELATED APPLICATIONS

This application is a Divisional patent application of application Ser.No. 11/979,079, filed on 31 Oct. 2007 now U.S. Pat. No. 7,443,074 whichis a Divisional patent application of Ser. No. 11/281,427, filed on 18Nov. 2005 now U.S. Pat. No. 7,356,906 which is a Divisional patentapplication of Ser. No. 10/492,176 filed on 9 Apr. 2004, now U.S. Pat.No. 6,992,419.

TECHNICAL FIELD

The present invention relates to a radial core type brushlessdirect-current (BLDC) motor, and more particularly, to a brushlessdirect-current (BLDC) motor having a radial core type double rotorstructure in which double rotors are disposed in the inner and outersides of a stator, respectively in a radial core type motor, to therebyenable a complete division of a stator core and thus enhanceproductivity of coil windings and a motor output.

BACKGROUND ART

A BLDC motor can be classified into a core type (or radial type) and acoreless type (or axial type), each having a generally cup-shaped(cylindrical) structure, according to whether or not a stator coreexists.

A BLDC motor of a core type structure is classified into an internalmagnet type of FIG. 2 including a cylindrical stator where coils arewound on a number of protrusions formed on the inner circumferentialportion thereof in order to form an electronic magnet structure, and arotor formed of a cylindrical permanent magnet, and an external magnettype of FIG. 1 including a stator where coils are wound up and down on anumber of protrusions formed on the outer circumferential portionthereof, and a rotor formed of a cylindrical permanent magnet on theouter portion of which multiple poles are magnetized.

In the external magnet type BLDC motor as shown in FIG. 1, stator cores101 a around which coils (not shown) are wound are installed on the baseof a stator through a supporter, respectively. A cup-shaped rotor 101 cis installed through a central rotational shaft 101 d, in which therotor 101 c is freely rotated through a bearing installed on the centerof the stator, and a cylindrical permanent magnet 101 b is attached tothe inner circumferential portion of the rotor, to form a predeterminedcrevice, that is, a gap G with respect to the stator.

When power is applied to the FIG. 1 motor, a magnetic field is createdaround the coils wound on the stator cores 101 a of the stator.Accordingly, a rotor case is rotated by a mutual action with a magneticflux by the permanent magnet 101 b mounted on the rotor 101 c.

In the conventional BLDC motor, a main path of the magnetic flux is amagnetic circuit which forms a closed circuit starting from thepermanent magnet and proceeding toward the permanent magnet again and ayoke via the gap and the stator core of the stator.

In the internal magnet type BLDC motor as shown in FIG. 2, a pluralityof T-shaped core portions 202 c on a stator core around which coils arewound, protrude inwards. Also, the inner sides of the respective coreportions form a cylinder of a predetermined diameter. Also, a rotor 202f having a cylindrical permanent magnet including a rotational shaft 202d, or a ring-shaped permanent magnet 202 b attached to a cylindricalyoke 202 including a central rotational shaft, is mounted in the innerportion of the cylinder surrounded by the core portions 202 c. Theinternal magnet type BLDC motor rotates in the same manner as that ofthe external magnet type BLDC motor.

The magnetic circuit in the above-described core type BLDC motor has asymmetrical structure in the radial direction around the rotationalshaft. Accordingly, the core type BLDC motor has less axial vibratorynoise, and is appropriate for low-speed rotation. Also, since a portionoccupied by a gap with respect to the direction of the magnetic path isextremely small, a high magnetic flux density can be obtained even if alow performance magnet is used or the number of magnets is reduced. As aresult, a big torque and a high efficiency can be obtained.

However, such a yoke structure causes loss of a yoke material whenfabricating a stator. In addition, a special-purpose expensive dedicatedwinding machine must be used for winding coils around the yoke duringmass-production, because the yoke structure is complicated. Also, sincea mold for fabricating a stator is expensive, initial investment costsbecome high.

Meanwhile, in order to improve the shortcomings of the above-describedcore type BLDC motor, a conventional coreless type BLDC motor proposedby the same applicant as that of the present invention is disclosed inU.S. Pat. No. 5,945,766, as an axial type which is a double rotor typeBLDC motor for offsetting axial vibration generated when rotors rotateand simultaneously increasing a torque more than two times.

Between first and second rotors is installed a stator in the aboveconventional coreless type BLDC motor is installed at a distance by apredetermined gap with respect to the first and second rotors. Aroundthe stator are wound a plurality of bobbin-less coils for applying anelectromagnetic force to the first and second rotors in response to anapplied DC current. Also, current is applied to the coils so thatmagnetic fluxes which have identical axial polarities are generated whenmagnets corresponding to the first and second rotors have oppositepolarities, and current is supplied to the first and second rotors sothat electromagnetic forces are generated in the opposing directions toeach other.

In the case of the axial double rotor type BLDC motor, a stator isdisposed in the middle of the first and second rotors, in a manner thata magnetic circuit of a symmetrical structure is formed with respect tothe stator and the rotational shaft. Accordingly, because of the firstand second rotors and the stator, the number of stator coils areincreased two times and the number of field magnets are also increasedtwo times as many as a single rotor structure. Therefore, drivingcurrent and magnetic flux density are increased two times. As a result,the axial double rotor type BLDC motor can obtain torque at least twotimes as much as an identical axial single rotor structure.

The axial coreless type motor has various kinds of merits. However,since a portion occupied by armature windings includes an air gap, amagnetic resistance is high and thus a magnetic flux density is low incomparison with the number of magnets.

In other words, in the case of a magnetic circuit formed by magnets m1to m4 as shown in FIG. 3, a magnetic resistance is increased verylargely at an air gap G formed between magnets m1 and m2 and betweenmagnets m3 and m4, and thus a loss of the magnetic flux occurs. As aresult, an efficiency of the motor is lowered.

Also, it requires that an air gap become wider in order to increase thenumber of turns of armature windings for implementing a high torquemotor. For this reason, a magnetic flux density would rather decrease,and thus a motor efficiency further decreases.

Thus, the axial coreless type motor should use higher performancemagnets and the more number of magnets, in comparison with a radial coretype motor of an equivalent output, and finally may raise productioncost.

However, although the axial coreless gap type motor has theabove-described various kinds of advantages, it is in a moredisadvantageous position than a radial type motor, in view of axialvibration.

Meanwhile, in the case of a radial core type motor, a special-purposededicated winding machine should be used for winding coils around theabove-described integrated stator core. Accordingly, there have been anumber of proposals in order to solve the problems that the initialinvestment cost becomes very high, and productivity of winding coilsaround the stator core is low.

For example, in order to separate inner/outer wheels forming a core inan internal magnet type core motor, a stator structure has been alteredfrom an integration type to a division type, to thus facilitate windingof coils, or a coil winding method for cores has been altered withoutchanging an integration type core structure, to thus enhance workabilityin winding coils.

Meanwhile, an inner/outer double rotor type motor has been proposed fora radial core type motor. However, this motor has only intended tosimply increase the number of permanent magnets and utilize an emptyspace, to thereby enhance a motor output, and the stator structure hashad still an integration structure. Thus, the existing problems of thelow coil winding workability, the high material loss, the highinvestment cost for the winding machine, etc., still remain, and thecoil windings should be provided doubly at the inner/outer sides of thestator core.

Also, a winding machine for winding coils at the inner side of the coreand that for winding coils at the outer side of the core cannot becommonly used. As a result, the investment cost for winding machinesincreases as much as an increase in the motor output.

In addition to the above-described conventional art, a plurality ofdivision type core structure motors have been proposed for a radial coretype motor, in order to increase productivity of winding coils of thestator core and reduce the investment cost for winding machines.

DISCLOSURE OF THE INVENTION

To solve the above problems, it is an object of the present invention toprovide a brushless direct-current (BLDC) motor having a radial coretype double rotor structure in which permanent magnet rotors aredisposed in the inner and outer sides of a stator core, respectively, tothus form a magnetic circuit by the inner and outer permanent magnetsand rotor yokes and to thereby enable a complete division of a statorcore and thus greatly enhance productivity of coil windings and a motoroutput.

It is another object of the present invention to provide a brushlessdirect-current (BLDC) motor having a radial core type double rotorstructure which can make the most of merits of an axial double rotortype and a radial core type and improve demerits thereof.

It is still another object of the present invention to provide abrushless direct-current (BLDC) motor having a radial core type doublerotor structure which can greatly enhance productivity of assembling astator by a stator structure capable of wiring coils by automaticallypositioning and fixing a plurality of stator core assemblies to a coresupport plate when employing a double rotor and division type statorcore structure.

It is yet another object of the present invention to provide a brushlessdirect-current (BLDC) motor having a radial core type double rotorstructure having an integrated double rotor structure which can enhancedurability and reliability by integrally molding the inner and outerrotors and bushings via an insert molding method using thermosettingresin.

It is yet still another object of the present invention to provide abrushless direct-current (BLDC) motor having a radial core type doublerotor structure adapted as a driving source of a drum for a washingmachine which requires waterproof by integrally molding a stator via aninsert molding method using thermosetting resin and combining the statortogether with the integrated double rotors.

It is a further object of the present invention to provide a method ofmanufacturing a brushless direct-current (BLDC) motor having a radialcore type double rotor structure.

To accomplish the above object of the present invention, according to anaspect of the present invention, there is provided a brushlessdirect-current (BLDC) motor having a radial core type double rotorstructure, the BLDC motor comprising: a rotational shaft which isrotatably mounted in a housing of the motor; double rotors including aninner rotor and an outer rotor in which a central portion of the innerrotor and the outer rotor is combined with the rotational shaft via abushing and is rotatably supported, a plurality of N-pole and S-polemagnets are disposed alternately in annular form on different concentriccircumferences in each rotor, and opposing magnets with a predetermineddistance between the inner and outer rotors are disposed to haveopposite polarities; and an integrated stator fixed to the housing ofthe motor, in which a plurality of stator core assemblies aretemporarily assembled to an annular core support plate enablingautomatic positioning and then are integrally formed into a single bodyin annular form via an insert molding using thermosetting resin, and amutually same air gap is formed between the inner and outer rotors, eachof said stator core assemblies being wound by coil around a bobbin whichincludes a plurality of division type stator cores, wherein a magneticcircuit is formed via the magnets disposed in opposite polarities in theinner and outer rotors and the division type stator cores positionedbetween the inner rotor and the outer rotor.

The integrated stator comprises: a number of division type stator cores;a number of insulation bobbins surrounding the number of division typestator cores; a number of coils wound around the outer circumference ofeach bobbin; an annular core support plate which accommodates andsupports the number of stator core assemblies on the upper surfacethereof with a predetermined interval where coils are wound around thebobbin and simultaneously wiring the number of coils by phase; anautomatic positioning and supporting unit which automatically positionsand supports the number of stator core assemblies to the core supportplate with the predetermined interval; and a stator support which moldsthe upper surface with thermosetting resin in order to integrate theannular core support plate to which the number of stator core assembliesare supported.

The automatic positioning and supporting unit comprises: inner and outerguide flanges which are vertically extended to the inner and outer sidesof the core support plate, for accommodating and supporting the lowerportions of the number of stator core assemblies therein; a number offirst coupling protrusions which are extended with an identical intervalfacing the upper ends of the inner and outer guide flanges, and disposedbetween the adjacent stator core assemblies when the number of statorcore assemblies are assembled on the core support plate, therebyrestricting the stator core assemblies from moving in thecircumferential direction; and a number of second coupling protrusionswhich are extended between the number of first coupling protrusions withan identical interval facing the upper ends of the inner and outer guideflanges, and are combined with first and second coupling grooves whichare vertically formed on the inner and outer sides of the stator corewhen the number of stator core assemblies are assembled on the coreplate, thereby restricting the stator core assemblies from movingforward and backward with respect to the axial direction, wherein thenumber of stator core assemblies are automatically positioned with apredetermined interval when being combined with the number of first andsecond coupling protrusions.

Also, the automatic positioning and supporting unit comprises: a numberof first coupling protrusions which are vertically extended to the innerside of the core support plate, with an identical interval, and disposedbetween the inner sides of the adjacent stator core assemblies when thenumber of stator core assemblies are assembled on the core supportplate, thereby restricting the stator core assemblies from moving in thecircumferential direction; and a number of second coupling protrusionswhich are vertically extended to the outer side of the core supportplate with an identical interval facing the number of first couplingprotrusions, and are disposed between the outer sides of the adjacentstator core assemblies when the number of stator core assemblies areassembled on the core plate, thereby restricting the stator coreassemblies from moving forward and backward with respect to thecircumferential and axial directions, wherein the number of stator coreassemblies are automatically positioned with a predetermined intervalwhen being combined with the number of first and second couplingprotrusions.

Further, the automatic positioning and supporting unit comprises: anumber of first and second coupling protrusions which are extended tothe lower portions of the inner and outer flanges in the number ofinsulation bobbins; and a number of first and second coupling groovesfacing each other with a predetermined interval on an identicalcircumference along the inner and outer sides so that the first andsecond coupling protrusions are combined on the bottom of the coresupport plate, wherein the number of stator core assemblies areautomatically positioned with a predetermined interval when beingcombined with the number of first and second coupling grooves.

The core support plate further comprises: a number of conductive linesprinted on the lower surface of the core support plate in order tomutually wire the number of coils by phase; and a number of couplingholes which are formed on the ends of each of the number of conductivelines, to penetrate the core support plate, and takes out the number ofboth ends of the coils from the number of stator core assemblies to thelower surface.

Also, the BLDC motor further comprises an extension portion which isextended in the central direction of the stator support bodies and usedto be coupled with the housing of the motor.

Meanwhile, the double rotors comprises: a first yoke frame whose innerend is connected to the bushing and a first bent portion of the otherend is perpendicularly bent to form a cup shape; a second yoke framewhich is integrally combined with the first yoke frame, and whose innerend is connected to the bushing and a second bent portion of the otherend is perpendicularly bent to maintain a predetermined distance withrespect to the first bent portion of the first yoke frame; a pluralityof first N-pole and S-pole magnets disposed alternately in annular formon the outer circumferential surface of the first bent portion; and aplurality of second N-pole and S-pole magnets disposed alternately inannular form on the inner circumferential surface of the second bentportion, in which magnets facing the plurality of the first N-pole andS-pole magnets are disposed to have opposite polarities.

Also, the double rotors comprises: an inner rotor having an inner yokeformed into a cylindrical shape, and a plurality of first N-pole andS-pole magnets which are disposed alternately in annular form on theouter circumferential surface of the inner yoke; an outer rotor havingan outer yoke having a relatively larger diameter than that of the inneryoke so as to maintain a predetermined distance from the inner yoke, anda plurality of second N-pole and S-pole magnets disposed alternately inannular form on the inner circumferential surface of the outer yoke, inwhich magnets facing the plurality of the first N-pole and S-polemagnets are disposed to have opposite polarities; and a rotor supportwhich is integrated in annular form other than the opposing magnets inthe inner and outer rotors, to simultaneously form a space where thestator is inserted between the inner and outer rotors, and is moldedwith thermosetting resin so that the inner end thereof is connected tothe outer circumferential surface of the bushing.

The motor according to the present invention has an integrated structurethat the rotor and stator are molded with thermosetting resin. Thus, themotor according to the present invention is appropriately used fordriving a washing machine drum.

According to another aspect of the present invention, there is provideda brushless direct-current (BLDC) motor having a radial core type doublerotor structure, the BLDC motor comprising: a rotational shaft which isrotatably mounted in a housing of the motor; double rotors including aninner rotor and an outer rotor in which a central portion of a yokeframe is combined with the rotational shaft via a bushing and isrotatably supported, a plurality of N-pole and S-pole magnets aredisposed alternately in annular form on different concentriccircumferences in each rotor, and opposing magnets with a predetermineddistance between the inner and outer rotors are disposed to haveopposite polarities; and an annular stator which is installed with anair gap between the inner and outer rotors.

According to still another aspect of the present invention, there isprovided a method of manufacturing a brushless direct-current (BLDC)motor having a radial core type double rotor structure, the BLDC motormanufacturing method comprising the steps of: molding a number ofT-shaped division type stator core by using a magnetic material; windingcoils around an insulation bobbin which can cover the outercircumference of the core; preparing a number of stator core assemblieswhere coils are wound by inserting a pair of T-shaped cores into thecoils-wound bobbin in both directions of the bobbin and bonding the pairof cores by caulking; preparing an integrated stator by aligning andfixing the number of the coils-wound stator core assemblies on a printedcircuit board (PCB), wiring coils, and molding the stator coreassemblies in an annular form by an insert molding method usingthermosetting resin; and assembling the integrated stator so as to bepositioned between the double rotors in which the inner rotor and outerrotor are aligned in a radial type.

According to yet another aspect of the present invention, there isprovided a method of manufacturing a brushless direct-current (BLDC)motor having a radial core type double rotor structure, the BLDC motormanufacturing method comprising the steps of: molding a number ofT-shaped division type stator core by using a magnetic material; windingcoils around a number of insulation bobbins which can cover the outercircumference of the core; preparing a number of stator core assemblieswhere coils are wound by inserting a T-shaped core into each of thecoils-wound bobbins; preparing an integrated stator by aligning andfixing the number of the coils-wound stator core assemblies on a anannular core support plate, wiring coils, and molding the stator coreassemblies in an annular form by an insert molding method usingthermosetting resin; and assembling the integrated stator so as to bepositioned between the double rotors in which the inner rotor and outerrotor are aligned in a radial type.

According to yet still another aspect of the present invention, there isprovided a method of manufacturing a brushless direct-current (BLDC)motor having a radial core type double rotor structure, the BLDC motormanufacturing method comprising the steps of: molding a number ofI-shaped division type stator core by using a magnetic material; moldingupper and lower insulation bobbins which are divided up and down so asto cover the outer circumference of the core; preparing a number ofdivision type stator core assemblies where coils are wound by wiringcoils around the assembled bobbins at the state of assembling the upperand lower bobbins into the upper and lower portions of the I-shapedcore; preparing an integrated stator by molding the coils-wound statorcore assemblies in an annular form by an insert molding method usingthermosetting resin; and assembling the integrated stator so as to bepositioned between the radial type double rotors.

According to a further aspect of the present invention, there isprovided a method of manufacturing a brushless direct-current (BLDC)motor having a radial core type double rotor structure, the BLDC motormanufacturing method comprising the steps of: integrally molding aninsulation bobbin having first and second flanges at both sides thereofand surrounding a middle portion an I-shaped stator core around whichcoils are wound by an insert molding method using thermosetting resin;preparing a number of stator core assemblies by winding coils betweenthe first and second flanges of the bobbin; wiring both ends of thecoils taken out to the lower surface of a core support plate at thestate of temporarily assembling the number of the stator core assemblieson a core support plate having a number of automatic positioningcoupling protrusions formed on the inner and outer ends thereof;preparing an integrated stator by molding the coils-wound stator coreassemblies other than the inner and outer sides of the division typestator core in an annular form by an insert molding method usingthermosetting resin; and assembling the integrated stator so as to bepositioned between the double rotors in which an inner rotor and anouter rotor are aligned in radial type.

According to a further still aspect of the present invention, there isprovided a method of manufacturing a brushless direct-current (BLDC)motor having a radial core type double rotor structure, the BLDC motormanufacturing method comprising the steps of: integrally molding abobbin on the outer circumference of a stator core by an insert moldingmethod using thermosetting resin, in such a manner that the stator coreis inserted into a hollow portion of a vessel portion of a bobbin, andat least one connection pin is inserted into the corners of first andsecond flanges opposing to each other in the bobbin; preparing a numberof stator core assemblies by winding coils between the first and secondflanges of the bobbin; mutually wiring coils by phase by connecting oneend of the coils to one end of the connection pin and connecting theother end of the connection pin taken out to the lower surface of thecore support plate to a conductive line printed on the lower surface ofthe core support plate, at the state of temporarily assembling thenumber of the stator core assemblies on a core support plate having anumber of automatic positioning coupling protrusions formed on the innerand outer ends thereof; preparing an integrated stator by molding thestator core assemblies other than the inner and outer sides of thedivision type stator core in an annular form by an insert molding methodusing thermosetting resin; and assembling the integrated stator so as tobe positioned between the double rotors in which an inner rotor and anouter rotor are aligned in radial type.

According to a further still aspect of the present invention, there isprovided a method of manufacturing a brushless direct-current (BLDC)motor having a radial core type double rotor structure, the BLDC motormanufacturing method comprising the steps of: integrally molding aninsulation bobbin having first and second flanges at both sides thereofin which first and second coupling protrusions are provided on the lowerend of the first and second flanges, and surrounding a middle portion anI-shaped stator core around which coils are wound by an insert moldingmethod using thermosetting resin; preparing a number of stator coreassemblies by winding coils between the first and second flanges of thebobbin; wiring both ends of each coil at the state of inserting andtemporarily assembling the first and second coupling protrusions of thenumber of the stator core assemblies into a number of mutually opposingautomatic positioning coupling holes formed concentrically on the innerand outer ends of an annular core support plate; preparing an integratedstator by molding the coils-wound stator core assemblies other than theinner and outer sides of the division type stator core in an annularform by an insert molding method using thermosetting resin; andassembling the integrated stator so as to be positioned between thedouble rotors in which an inner rotor and an outer rotor are aligned inradial type.

In this case, the double rotors are integrated in an annular form,respectively, except for the opposing magnets in the inner and outerrotors, and are molded with thermosetting resin so that the inner end isconnected to the outer circumference of the bushing, while forming aspace where the stator is inserted between the inner and outer rotors.

As described above, the present invention takes the merits of the doublerotor type BLDC motor, and thus provides a motor where a stator core isperfectly divided. That is, the BLDC motor according to the presentinvention takes the merits of increasing the output and torque andremoves the demerits of increasing the material cost caused by using ahigh-performance magnet material of the axial double rotor type motor,and takes the merits of causing the small axial vibration and removesthe demerits such as the high investment of expensive molds, the coilwinding cost caused by using an integrated single stator core, and thefacility investment cost caused by using a dedicated winding machine.

Also, it is possible to automatically position and fix a number ofstator core assemblies to a core support plate, to thereby easilymutually wire each coil and enhance productivity of assembling stators.

Also, the double rotors and the bushing are integrally molded by aninsert molding method using thermosetting resin, to thereby enhancedurability and reliability.

Also, the stator is integrally molded by using thermosetting resin, andthen combined with the integrated double rotors, thereby providing aBLDC motor appropriate for driving a drum of a washing machine.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other objects and advantages of the present invention willbecome more apparent by describing the preferred embodiments thereof inmore detail with reference to the accompanying drawings in which:

FIG. 1 is a cross-sectional view for explaining a structure of aconventional external magnet core type BLDC motor;

FIG. 2 is a cross-sectional view for explaining a structure of aconventional internal magnet core type BLDC motor;

FIG. 3 is a view for explaining a conventional axial gap type magneticcircuit;

FIGS. 4A through 4C are views for explaining a toroidal permanent magnethaving a gap;

FIG. 5 is a view for explaining a conventional magnetic circuit;

FIGS. 6A through 6D are views for explaining the structure andoperational principle of a radial core type double rotor BLDC motoraccording to a basic embodiment of the present invention, in which FIG.6A is a cross-sectional view schematically showing the BLDC motor cutalong the circumferential direction, FIG. 6B is a plan view showing theBLDC motor cut along the axial direction, FIG. 6C is a perspective viewshowing a divided stator core, and FIG. 6D is a perspective view showinga bobbin;

FIGS. 7A and 7B are plan views for comparing a magnetic circuitaccording to the present invention with that of the existing externalmagnet radial core type motor;

FIG. 8 is a plan view showing a core arrangement when a shape of adivision type core is of a T-shape according to a variation of thepresent invention;

FIG. 9A is a front view of a radial core type double rotor BLDC motoraccording to a preferred embodiment of the present invention;

FIG. 9B is a cross-sectional view cut along line A-A of FIG. 9A;

FIG. 9C is a cross-sectional view cut along line B-B of FIG. 9A;

FIG. 10A is a perspective view of a perfect division type stator corewhich is used in the present invention;

FIG. 10B is a cross-sectional view cut along line A-A of FIG. 10A;

FIG. 11A is an exploded perspective view showing a relationship ofcoupling a stator core assembly and a core support plate according to afirst embodiment of the present invention;

FIG. 11B is a partially enlarged perspective view of a core supportplate;

FIG. 11C is an enlarged view showing a coupling state of the coresupport plate;

FIG. 12A is a bottom view of the core support plate of FIG. 11A;

FIG. 12B is an enlarged view of portion “A” in the core support plate ofFIG. 12A;

FIGS. 12C through 12F are cross-sectional views showing a mutual wiringstructure between the coils;

FIGS. 13A through 13D are views showing a second embodiment of thepresent invention, in which FIG. 13A is an exploded perspective viewshowing a relationship of coupling a stator core assembly and a coresupport plate, FIG. 13B is an enlarged perspective view of the coresupport plate, FIG. 13C is an enlarged view showing a coupling state ofthe core support plate, and FIG. 13D is a cross-sectional view cut alongline A-A of the division type stator core;

FIG. 14A is an exploded perspective view showing a relationship ofcoupling a stator core assembly and a core support plate according to athird embodiment of the present invention;

FIG. 14B is an enlarged view showing a division type stator core;

FIG. 15 is a perspective view showing an integrated stator according tothe present invention;

FIG. 16 is a cross-sectional view showing a support structure of doublerotors using a double yoke frame according to the present invention;

FIGS. 17A through 17D are cross-sectional views showing variations of acoupling structure of a double yoke frame, respectively;

FIGS. 18A and 18B are perspective views of a bushing which is used inthe present invention;

FIG. 18C is a cross-sectional view showing a coupling structure of abushing by a combination of a rivet and a connection pin;

FIG. 19A is a cross-sectional view of an integrated double rotor motorseen in an axial direction; and

FIG. 19B is a perspective view of FIG. 19A.

BEST MODE FOR CARRYING OUT THE INVENTION

Preferred embodiments of the present invention will be described indetail with reference to the accompanying drawings.

The present invention provides a motor structure which can realize adivision type core structure as a new motor of a double rotor structurein which an internal magnet type and an external magnet type arecombined. When permanent rotors are disposed at both sides of a statorin an axial gap type double rotor BLDC motor, an output is enhanced anda magnetic circuit is formed. The present invention applies advantagesof such an axial gap type double rotor BLDC motor to a radial core typedouble rotor BLDC motor.

Prior to describing the radial core type double rotor BLDC motoraccording to the present invention, an ideal magnetic circuit will bedescribed. In FIG. 4A, a toroidal magnet has a gap 1 g. When the gap 1 gis filled with an auxiliary magnetic material of a high permeability, itis assumed that the status of the magnet is positioned at a point “a” ona demagnetization curve of FIG. 4C. This position is a point having thehighest magnetic flux density Bm at the state where an external magneticfield is not present, and a state having the lowest magnetic resistance.

If the auxiliary magnetic material is removed from the gap, a magneticresistance (reluctance) of the magnetic circuit is increased sincepermeability of air is lower than that of the auxiliary magneticmaterial, and the statue of the magnet moves to a point “b” on the FIG.4C demagnetization curve. That is, a magnetic flux density Bm isdecreased.

The magnetic flux is present only in the magnet except for a gap. Themagnetic flux is uniformly distributed on the cross-section of themagnet. However, the magnetic flux is distributed with a littlescattering in the gap as shown in FIG. 4B. Thus, it will be regardedthat the cross-sectional area “Ag” of the gap is slightly larger thanthe cross-sectional area “Am” of the magnet.

When the ampere integration rule for the magnetic field is applied, thefollowing Equation 1 is obtained since there is no free current.Equation 1 is rewritten into Equation 2. Hm.times.1 m+Hg.times.1 g=0 (1)Hm=−1 g 1 m.times.Hg.function.[A.times./.times.m] (2)

It can be seen through Equation 2 that presence of the gap induces aneffect that a magnetic field of a direction opposing the magnetic fluxadvancing direction (that is, a demagnetization field) is applied in thepermanent magnet. Here, signs of Hm and Hg are opposite to each other.

Since the magnetic flux must be continuous throughout the whole circuit,the following Equation 3 is established. Also, a relationship betweenthe magnetic flux density and the magnetic field in a gap is expressedas Equation 4. Thus, Equation 5 can be obtained by Equations 1 through4. Bm.times. Am=Bg.times.Ag.function.[Wb] (3).times.Bg=.mu.0.times.Hg(4).times.Bm=−.mu.0.times.Ag Am 1 m 1 g.times.Hm.times.[T] (5)

Here, .mu..sub.0 denotes permeability of vacuum or air, and has a valueof 4.pi..times.10.sup.−7 [N/A.sup.2] or 4.pi..times.10.sup.−7 [H/m] inthe SI unit system, that is a coefficient representing a relationshipbetween a magnetic field and a magnetic flux density distributed in thespace. The permeability of ferromagnetic materials such as iron amountsabout 5000.mu..sub.0. The magnetic resistance Rm is expressed as 1/.mu.Sin which 1 denotes length of the magnetic circuit through which themagnetic flux passes, .mu. denotes permeability, and S denotesacross-sectional area. Here, it can be seen that permeability isinversely proportional to the magnetic resistance.

Equation 5 represents a straight line (0, b) of FIG. 4C, in which anintersection “b” with the demagnetization curve represents a magneticstate where an auxiliary magnetic material has been removed (that is, anoperating point). A value representing slope of the straight line iscalled a permeance coefficient.

By the above analysis, it can be seen that the operating point of apermanent magnet is determined by a shape of a magnet and ademagnetization curve. However, since the actual situation is far fromthe ideal case, a more realistic situation as shown in FIG. 5 can beconsidered.

A portion occupied by a magnet 105 a in a magnetic circuit is verysmall. A path through which most magnetic fluxes pass, that is, a polepiece is made of a material of low magnetic resistance and highpermeability. The magnetic circuit includes a gap in which an auxiliarymagnetic material 105 b is inserted. Thus, most fluxes .PHI. g among thewhole magnetic flux .PHI. m generated by the magnet 105 a passes throughthe pole piece 105 c. If the auxiliary magnetic material 105 b isremoved, a small number of fluxes are leaked and do not pass through thegap. As a result, as shown in FIG. 5, leaking fluxes .PHI. l passthrough the space formed between the upper and lower pole pieces 105 c.To represent the above leaking situation, a leakage coefficient q mustbe included as expressed as Equation 6.B.sub.mA.sub.m=qB.sub.gA.sub.g[Wb] (6)

The leakage coefficient q is defined as (flux in a magnet)/(flux in agap). A relationship between Bm and Hm is defined as Equation 7.Bm=−.mu.0.times.q.times..times. Ag.times.1 m Am.times.1 g Hm.function.[T] (7)

The following facts can be seen from the above-described Equations.

A status of a permanent magnet, that is, an operating point isdetermined by a demagnetization feature that is an inherent feature of amagnet, size of the magnet, and construction of a magnetic circuit.

If other conditions are same, a magnetic flux density at an operatingpoint becomes large as a magnet is magnetized in a lengthy direction andan area of a surface perpendicular to the magnetization directionbecomes small.

When a portion of a large magnetic resistance is present in part of amagnetic circuit, a magnetic flux density is decreased. When length of agap becomes wide, the magnetic flux density is decreased.

As a magnetic resistance in a magnetic circuit becomes large, a magneticflux density is decreased, and a magnetic field Hm of acounter-direction with respect to the magnetic flux in the magnet thatis called a demagnetization field becomes large.

Thus, the present invention provides a BLDC motor having merits of easymanufacturing, easy winding, and small loss of materials, based on theabove-described principle, in which the BLDC motor is manufactured bydividing a stator core instead of forming a magnetic circuit bydisposing permanent magnet rotors at the inner and outer sides of astator.

Hereinbelow, first of all, the structure and operational principle of amotor according to the present invention will be described, andembodiments of manufacturing a stator will be described. Then, the mostpreferable embodiment of a commercialized motor according to the presentinvention, a stator structure and various manufacturing methods thereofwill be described.

FIGS. 6A through 6C are views for explaining the structure andoperational principle of a radial core type double rotor BLDC motoraccording to the present invention, in which FIG. 6A is across-sectional view schematically showing the BLDC motor, FIG. 6B is aplan view showing the BLDC motor, and FIG. 6C is a perspective viewshowing a single stator core. FIGS. 7A and 7B are plan views forcomparing a magnetic circuit according to the present invention withthat of the existing radial core type motor.

Referring to FIGS. 6A through 6C, in a radial core type double rotorBLDC motor according to the present invention, a pair of double rotors 5including an inner rotor 5 a and an outer rotor 5 b are combined with astator support frame, for example, a rotational shaft 9 that isrotatably supported to the center of a housing through two bearingspreferably in the housing 2 in the body of the motor, and an integratedannular stator 3 is disposed between the double rotors 5.

An annular inner yoke frame 8 a and an annular outer yoke frame 8 b arepreferably integrally formed in the double rotors 5, and supported tothe rotational shaft 9. A number of magnets 16 a-16 d and 17 a-17 d aredivisionally magnetized on the opposing surface of the inner yoke frame8 a and the outer yoke frame 8 b, or a number of divided magnets aremounted thereon. A number of opposing magnets 16 a-16 d and 17 a-17 dpositioned in the facing surface of the inner yoke frame 8 a and theouter yoke frame 8 b, are disposed to have different polarities.Simultaneously, adjacent opposing magnets are disposed to have differentpolarities.

Also, a predetermined gap is formed between the opposing magnets in thedouble rotors. A number of division type stator cores 3 a (23 a-23 d)are disposed in the annularly disposed stator 3. A coil 3 b (13 a-13 d)is individually wound around each division type stator core 23 a-23 d.The number of division type stator cores 23 a-23 d are fixed by statorsupport materials 3 e that is injection-molded in thermosetting resin toaccomplish a fixed annular shape.

As shown in FIG. 6C, the division type stator cores 23 a-23 d are madeof a number of silicon steel plates laying a silicon steel plate overanother, or by sintering a soft magnetic compound having high permeanceand high electrical resistance, in order to prevent loss of a magneticflux due to eddy current that can occur during rotation of a motor. Inthis case, the shape of the core can be made more freely.

Prior to describing the function of the radial core type double rotorBLDC motor having the above-described structure according to the presentinvention, a magnetic circuit in an external magnet type motor among theconventional radial core type motors as shown in FIG. 1 will bedescribed with reference to FIG. 7B. When power is applied to coils in amotor of an integrated core structure, a magnetic field is formed in thecoils wound around a stator core 1 a, to thus make a rotor casing rotateby an interaction with the magnetic flux generated from a permanentmagnet 1 b installed in the rotor 1 c.

Here, in the case of the integrated core type motor as shown, a salientpole and another salient pole 1 e in a core portion of a low magneticresistance must be connected to each other and formed integrally, inorder to maintain a flow of a magnetic path along an arrow direction A1formed to pass through the integrated stator core 1 a, the magnet 1 band the yoke in the rotor.

Thus, since coils are wound around a T-shaped core portion in theintegrated core type motor, by using a dedicated winding machine, amanufacturing cost and an installation cost become high to thus weakenthe competitiveness. Also, since a core shape is complicated and largein the conventional integrated radial core type motor, a material lossbecomes large and a winding work becomes difficult.

Meanwhile, as shown in FIG. 7A, a divided core type motor according tothe present invention forms a magnetic circuit along an arrow directionA10 in sequence with a magnet 16 a, an inner yoke frame 8 a, a magnet 16b, and a stator core 23 b in an inner rotor 5 a, and a magnet 17 b, anouter yoke frame 8 b, a magnet 17 a, and a stator core 23 a in an outerrotor 5 b.

That is, since the permanent magnets 16 a-16 d and the yoke frame 8 a inthe inner rotor 5 a play a role of salient poles in the integrated coretype motor, the stator core 3 a need not be of an integrated type. Thus,the present invention enables the stator core to be fabricated with anumber of individual cores 23 a-23 d.

As a result, since a division type core is small, a loss of siliconsteel plate is small. Thus, since a material loss for the division typecore is little, and a shape of the division type core is simplified, itcan be easily fabricated. Also, since coils can be wound around thedivided cores 23 a-23 d by using a general purpose winding machine, aninvestment cost for winding coils and purchasing a winding machine isreduced.

As shown in FIG. 6C, a stator fabrication method according to thepresent invention includes the steps of molding an I-shaped stator core3 a by using a silicon steel plate, and separating the molded I-shapedstator core 3 a into upper and lower portions to then be stacked intotwo T-shaped cores 23 e and 23 f, or separating a soft magnetic powdersintered product into upper and lower portions and fabricating adivision type core 3 a.

Thereafter, as shown in FIG. 6D, coils are wound around an insulatorbobbin 30 by a general transformer manufacturing method. Then, oneseparated part 23 e of a T-shaped core is inserted into one side of thebobbin 30 and the other separated part 23 f of the T-shaped core isinserted into the other side of the bobbin 30. These two parts of theT-shaped core are bonded by a caulking process, to complete a statorcore assembly around which coils are wound. Then, the stator coreassemblies around which a number of coils have been wound are disposedand fixed on a PCB and the coils are wired. Thereafter, at the statewhere the PCB on which the stator core assemblies have been disposed inannular form into a mold (not shown), thermosetting resin is injected byan injection molding method such as an insert molding method, to therebyobtain an annular integrated stator according to the present invention.

Another method of manufacturing a stator according to the presentinvention will be described below with reference to FIG. 8.

First, division type stator cores 24 a-24 h are fabricated in theT-shaped form. Then, as shown in FIG. 6D, coils 13 a-13 d are woundaround a number of insulator bobbins 30. Then, the separated T-shapedcores 24 a, 24 c, 24 e and 24 g are inserted into the bobbins 30 fromupwards, and the separated T-shaped cores 24 b, 24 d, 24 f and 24 h areinserted into the bobbins 30 from downwards, to thus complete a statorcore assembly around which a number of coils have been wound.

Then, in the same manner as the above-described embodiment, the statorcore assemblies around which a number of coils have been wound aredisposed and fixed on a PCB or a core support and the coils are wired.Thereafter, at the state where the PCB on which the stator coreassemblies have been disposed in annular form into a mold (not shown),thermosetting resin is injected by an injection molding method such asan insert molding method, to thereby obtain an annular integrated statorsimilar to the above-described embodiment according to the presentinvention.

In FIG. 8, the bobbin 30, the coils 3 b wound around the bobbin 30, andthe stator support 3 e formed of resin have been omitted in order toillustrate a core structure of the stator cores 24 a-24 h.

As still another stator manufacturing method, an I-shaped integratedcore is fabricated as shown in FIG. 6C, and then the bobbin which hasbeen divided into upper and lower bobbins 30 i and 30 j as shown in FIG.6D. Thereafter, the divided bobbins 30 i and 30 j are assembled into theI-shaped core 3 a, and then coils 3 b are wound around the assembledbobbins 30 i and 30 j, to thereby prepare a number of stator coreassemblies around which the coils have been wound.

Then, in the same manner as the above-described embodiment, the statorcore assemblies around which a number of coils have been wound aredisposed and fixed on a PCB and the coils are wired. Thereafter, at thestate where the PCB on which the stator core assemblies have beendisposed in annular form into a mold (not shown), thermosetting resin isinjected by an injection molding method such as an insert moldingmethod, to thereby obtain an annular integrated stator similar to theabove-described embodiment according to the present invention.

As described above, although the bobbin applied in the above-describedembodiments has been described as having a divided structure, a numberof bobbins can be of an annular form to then make both ends thereofconnected to each other.

Thereafter, a rotational shaft 9 and an integrated double rotor 5 arecombined with the completed integrated stator 3, to thereby complete aradial core type double rotor BLDC motor of a divided core structure.

Hereinbelow, a commercialized BLDC motor according to a preferredembodiment of the present invention will be described.

FIG. 9A is a front view of a radial core type double rotor BLDC motoraccording to a preferred embodiment of the present invention. FIG. 9B isa cross-sectional view cut along line A-A of FIG. 9A. FIG. 9C is across-sectional view cut along line B-B of FIG. 9A.

Referring to FIGS. 9A to 9C, the BLDC motor is installed on the lowerportion of a washing machine and has a structure appropriate for drivingthe drum of the washing machine in the left and right directions, but isnot limited thereto.

That is, in the case of the BLDC motor 1 shown in FIG. 9C, the innercircumferential portion of a core support plate 4 is supported on ahousing 2 of the washing machine by a variety of coupling elements suchas a bolt/nut. The BLDC motor 1 includes a stator 3 where a number ofcompletely divided stator cores 3 a are assembled in annular form inwhich coils 3 b are wound around the outer circumference of a bobbin(not shown), a rotor 5 of a double rotor structure where a number ofmagnets 6 a and 6 b are disposed in annular form with a predeterminedmagnetic gap on the inner and outer circumferences of the stator 3 andan inner rotor 5 a and an outer rotor 5 b are supported to a yoke frame8, and a rotational shaft 9 which is rotatably supported to the housing2 via a bearing 11 and connected to the center of the yoke frame 8 via abushing 7.

The stator 3 is integrally formed of thermosetting resin in annular formby an insert molding method, at the state of temporarily assembling anumber of stator core assemblies 3 c of FIG. 11C in which coils 3 b arewound around the outer circumference of a bobbin (not shown) with anannular core support plate 4 including an automatic positionsetting/supporting unit, which will be described later.

In this case, the stator support 3 e formed by the insert molding methodfor the number of stator core assemblies is inserted between the numberof stator core assemblies to integrate the number of stator coreassemblies 3 c. An extension 40 a which is extended inwards from thecore support plate 4 at the time of performing the insert molding methodplays a role of fixing the housing 2 of the washing machine andsimultaneously blocking water leaked from the washing machine fromflowing into the motor.

Also, the core support plate 4 includes a variety of automatic positionsetting/supporting units to be described later. Accordingly, when anumber of stator core assemblies 3 c are assembled on the core supportplate 4, an assembly position is automatically determined andsimultaneously easily temporarily assembled for an insert moldingmethod, to thereby enhance an assembly workability.

In FIG. 9C, a reference numeral 12 denotes a Hall IC assembly forgenerating a position signal detecting position of a rotor 5 rotating inorder to control a current supply for a 3-phase driving type statorcoil. Accordingly, as shown in FIGS. 9C and 19A, an inner yoke 51 a inan inner yoke frame 8 a in the inner rotor 5 a is not extended to thelower end of the inner magnet 6 a and a portion opposing the Hall IC inthe Hall IC assembly 12 has been removed.

A reference numeral 10 denotes a cooling hole.

Since the rotor 5 of the double rotor structure is rotated by the stator3 in the motor 1 in the same manner as that of the FIG. 6 embodiment,the detailed description thereof will be omitted.

That is, since the magnets 6 a and 6 b of the inner rotor 5 a and theouter rotor 5 b and the division type stator core 3 a form a singlecomplete magnetic circuit, it is possible to completely divide a statorcore. Thus, the present invention can divide a stator core into a numberof division type stator cores 3 a, and also increase a motor output andtorque by employing a double rotor.

However, when a stator core is divided into a number of division typestator cores 3 a, a coil winding productivity for an individual statorcore 3 a is remarkably superior to the case of using an integrated, thatis, single stator core, but an assembly productivity thereof and adurability thereof can be inferior thereto.

Hereinbelow, a structure of enhancing an assembly productivity and adurability of the assembled product of a radial core type double rotorBLDC motor 1 according to the present invention will be described indetail.

FIG. 10A is a perspective view of a perfect division type stator corewhich is used in the present invention. FIG. 10B is a cross-sectionalview cut along line A-A of FIG. 10A. FIG. 11A is an exploded perspectiveview showing a relationship of coupling a stator core assembly and acore support plate according to a first embodiment of the presentinvention. FIG. 11B is a partially enlarged perspective view of a coresupport plate. FIG. 11C is an enlarged view showing a coupling state ofthe core support plate.

As shown in FIGS. 10A and 10B, a division type stator core 3 a is formedof a substantially I-shaped form. As shown, coupling grooves 31 a and 31b whose sectional areas are of shapes of a semi-circle are verticallyformed at opposing positions on both side surfaces. A bobbin 30 made ofan insulation material such as a plastic material is combined on theouter circumferences of the side surfaces. A hollow vessel is formed inthe middle portion of the bobbin 30, and flanges 30 a and 30 b areextended on the inner and outer sides of the vessel portion,respectively. A space in which coils 3 b are wound is formed between theflanges 30 a and 30 b.

Also, the bobbin 30 is injection-molded with a general plastic material.In the present invention, connection pins 32 are inserted between theindividual stator core assemblies for mutual connection of the woundcoils 3 b by phase (see FIG. 11C), or throughholes 33 through whichcoils pass can be formed at one side, both sides, or crossed position ofthe inner flange 30 a in the bobbin.

In this case, it is preferable that an assembly between the I-shapedstator core 3 a and the bobbin 30 is integrally molded by an insertmolding method using thermosetting resin. However, the present inventionis not limited thereto but can be assembled in the well-known method.

Also, the inner and outer flanges 30 a and 30 b is formed of arelatively smaller area than the outer opposing surface of the inner andouter extensions 34 a and 34 b in the I-shaped stator core 3 a. Inparticular, the lower ends of the inner and outer extensions 34 a and 34b in the stator core 3 a are distant by a predetermined distance fromthe lower ends of the inner and outer flanges 30 a and 30 b,respectively. The exposed portions which are not covered with the innerand outer extensions 34 a and 34 b of the stator core 3 a in the innerand outer flanges 30 a and 30 b are accommodated and supported by innerand outer guide flanges 41 and 42 in the core support plate to bedescribed later.

Meanwhile, a number of stator core assemblies 3 c shown in FIG. 11C areassembled in the present invention and an annular core support plate 4is used as shown in FIG. 11B in order to mutually wire both ends of thecoils 3 b. The core support plate 4 has a structure that a pair of innerand outer guide flanges 41 and 42 are vertically extended from anannular plate 40 toward one lateral direction of the inner and outersides of the annular plate 40, that is, upwards, to thus accommodate andsupport the lower portion of the individual stator core 3 a. That is,the exposed portions which are not covered by the inner and outerextensions 34 a and 34 b of the stator core 3 a in the inner and outerflanges 30 a and 30 b of the bobbin 30 are accommodated and supported ina space 43 between the inner and outer guide flanges 41 and 42.

Further, in order to automatically determine an assembly position andsimultaneously maintain a support state when a number of stator coreassemblies 3 c are assembled in the upper ends of the inner and outerguide flanges 41 and 42, a number of first coupling protrusions 44 a and44 b whose cross-sections are rectangular and a number of secondcoupling protrusions 45 a and 45 a whose cross-sections aresemi-circular are extended at a predetermined interval in the inner andouter guide flanges 41 and 42. In this case, the first and secondcoupling protrusions 44 a and 45 a in the inner guide flange 41 areopposed to the first and second coupling protrusions 44 b and 45 b inthe outer guide flange 42, respectively.

Thus, as shown in FIG. 11C, in each of the number of stator coreassemblies 3 c, the second coupling protrusions 45 a and 45 b arecombined with the coupling grooves 31 a and 31 b whose cross-sectionsare semi-circular in the stator core 3 a, and the first couplingprotrusions 44 a and 44 b are combined between the adjacent stator coreassemblies 3 c.

As a result, in the case that a number of stator core assemblies 3 c areassembled by using the core support plate 4, the assembly positions inthe radial direction and circumferential direction of the stator coreassemblies 3 c are automatically determined by the first couplingprotrusions 44 a and 44 b and the second coupling protrusions 45 a and45 b. Thus, an unskilled labor can assemble the number of stator coreassemblies with the core support plate 4. At the same time, since asupport state for an insert molding method can be easily maintained atthe following steps, an assembly productivity is very excellent.

Also, since the inner and outer extensions 34 a and 34 b in the statorcore 3 a form the inward and outward curved surface with a predeterminedcurvature, respectively, in the temporarily assembled stator 3 d, afullness of a circle combined with the inner and outer circumferences ofthe stator core assemblies 3 c becomes high, and thus a predeterminedclose magnetic gap can be maintained between the inner rotor 5 a and theouter rotor 5 b which are combined with the inner and outer portions ofthe stator 3 d.

A reference numeral 46 in FIG. 11B denotes throughholes for fixing thestator core assemblies 3 c to the core support plate 40 in which thestator support body 3 e made of thermosetting resin communicates theupper and lower portions of the core support plate 40 and integrallyformed during performing an insert molding method as shown in FIG. 9C. Areference numeral 47 denotes pin connection holes through whichconnection pins 32 are combined to mutually connect the coils 3 b.

Meanwhile, in the case that a number of stator core assemblies 3 c areassembled by using the cores support plate 4, a number of conductivelines 48 are disposed slantly on the bottom surface of the core supportplate 4 as shown in FIGS. 12A and 12B, from the pin connection holes 47a which are disposed on the outer circumference to the pin connectionholes 47 b which are disposed on the inner circumference via theadjacent pin connection hole, in order to connect both ends of the coils3 b by each phase. In this case, a number of conductive lines 48 areformed of a structure contained in the recessed grooves, respectively(see FIG. 12C). The pin connection holes 47 a and 47 b are installed topenetrate the center of circular connection pads 49 which are disposedat both ends of the conductive lines 48. However, it is possible only toform a coil guidance recessed groove instead of the conductive lines.

FIGS. 12C through 12F are cross-sectional views showing a mutual wiringstructure between the coils.

As shown in FIG. 12C, in the case of a first coil wiring method betweenthe coils 3 b, a pair of connection pins 32 are integrally inserted intothe bobbin 30 in the stator core assemblies 3 c by an insert moldingmethod. In this case, one end and the other end of the coils 3 b areconnected to the lower end of the connection pin 32 in advance. Then,the connection pins 32 in the stator core assemblies 3 c are insertedand assembled into the pin connection holes 47 a an 47 b in the coresupport plate 4, and the conductive lines 48 formed on the bottomsurface of the core support plate and the connection pins 32 are fixedby soldering, to thus connect coils 3 b.

As shown in FIG. 12D, in the case of a second coil wiring method, oneend of the coils in the stator core assemblies 3 c is passed through thethroughholes 33 formed in the flange 30 a in the bobbin and insertedinto the pin connection holes 47 a and 47 b in the core support plate 4.Each end of the coils and the conductive lines 48 are fixed bysoldering, to thus connect the coils 3 b.

As shown in FIG. 12E, in the case of a third coil wiring method, oneconnection pin 32 is integrally inserted into the bobbin 30 in thestator core assemblies 3 c, by an insert molding method, and one end ofthe coils 3 b is connected to the lower end of the connection pins 32 inadvance.

Thereafter, the connection pins 32 in the stator core assemblies 3 c areinserted and assembled into the pin connection holes 47 a in the coresupport plate 4, one end of the coils is passed through the throughholes33 formed in the flange 30 a in the bobbin and inserted into the pinconnection holes 47 b and 47 b in the core support plate 4. The coilsare wound around the connection pins 32, along the coil guidancerecessed groove, and wired with each other, to thus connect the coils 3b.

As shown in FIG. 12F, in the case of a fourth coil wiring method, bothends of the coils in the stator core assemblies 3 c is passed throughthe throughholes 33 formed in the flange 30 a in the bobbin and insertedinto the pin connection holes 47 a and 47 b in the core support plate 4.Both ends of the coils are fixed by soldering, to thus connect the coils3 b.

As described above, since the present invention performs a coil wiringbetween the stator core assemblies 3 c by passing through the pinconnection holes 47 a and 47 b in the core support plate 4 and bysoldering at the other end as shown in FIGS. 12C to 12F, a windingportion and a wiring portion on the core are separated to thus enhancean insulation performance.

Also, a number of conductive lines 48 formed on the bottom surface ofthe core support plate 4 and the corresponding wiring guidance recessedgrooves or printed wiring guidance lines are disposed by phase along thepositions of the coils to be wired. Thus, a person solders theconnection pins 32 or coils 3 b having passed through the pin connectionholes 47 a and 47 b to the end of the conductive lines 48 (see FIGS. 12Cand 12E). Otherwise, when coils are wired along the guidance recessedgrooves or printed wiring lines, any worker can easily wire the coilsand the conductive lines 48.

Hereinbelow, an assembly process of the stator 3 according to a firstembodiment of the present invention will be described.

First, each stator core 3 a is inserted into a hollow vessel of thebobbin 30, and integrally molded by an insert molding method so that atleast one connection pin 32 is inserted into the corner portion of theflanges 30 a and 30 b in the bobbin.

Thereafter, coils 3 b are wound around the outer circumferences of theflanges 30 a and 30 b in the bobbin 30 which is integrally molded withthe stator core 3 a, by using a general-purpose winding machine, tothereby prepare a number of stator core assemblies 3 c.

Then, a number of stator core assemblies 3 c are combined on the upperportion of the core support plate 4 which has been injection-molded asshown in FIG. 11A, and both ends of the coils are wired by phase on thebottom surface of the core support plate 4 according to the coil wiringmethod, to thus obtain the stator 3 d as shown in FIG. 11C.

Meanwhile, when the temporarily assembled stator 3 d of FIG. 11C is usedas a driving motor for a washing machine, the intensity thereof is weakto endure a magnetic force generated during running a washing machine.Also, in order to consistently maintain an air gap between the inner andouter magnets and the core, it is necessary to assume a concentricity.

For this purpose, except for the outer opposing surfaces of the innerand outer extensions 34 a and 34 b in each stator core 3 a, the lowersurface of the stator core 3 a is molded with thermosetting resin, forexample, BMC (Bulk Molding Compound) such as polyester, so that a spacebetween a number of stator core assemblies 3 c and a coil wiring portionin the lower portion of the core support plate 4 are covered, to therebyobtain a stator 3 shown in FIGS. 9C and 15. In this case, the extension40 a connected with the stator support 3 e located in the lower portionof the core support plate as shown in FIG. 9C is integrally molded to beused for coupling with the housing 2.

In FIG. 15, a reference numeral 12 denotes a Hall IC assembly.

As described above, a stator molded with an insulation material on thewhole surface is used for a washing machine. Thus, the motor adoptingthe stator according to the present invention can be used in a washingmachine which operates at a high humidity condition during washingwithout requiring an additional insulation material. Also, sharp edgeswhich can hurt workers are hidden to thus assuring a safety.

FIGS. 13A through 13D are views showing a second embodiment of thepresent invention, in which FIG. 13A is an exploded perspective viewshowing a relationship of coupling a stator core assembly and a coresupport plate, FIG. 13B is an enlarged perspective view of the coresupport plate, FIG. 13C is an enlarged view showing a coupling state ofthe core support plate, and FIG. 13D is a cross-sectional view cut alongline A-A of the division type stator core of FIG. 13A.

Referring to FIGS. 13A to 13D, a stator according to a second embodimentof the present invention is shown. Here, a cross-sectional structure ofa division type stator core 3 a′ differs from that of the firstembodiment. That is, the vertically formed coupling grooves are notformed in both lateral surfaces of the core 3 a′, but a number of firstand second coupling protrusions 44′ and 45′ for automaticallypositioning and supporting a number of stator core assemblies 3 c′ to anannular core support plate 4′ are vertically extended directly from anannular plate 40 without having inner and outer guide flanges.

The core support plate 4′ of the second embodiment includes a number offirst coupling protrusions 44′ whose cross-section is rectangular whichis formed at a predetermined interval concentrically inwards from theannular plate 40, and a number of second coupling protrusions 45′ whosecross-section is cross-shaped opposing the number of first couplingprotrusions 44′ formed at a predetermined interval concentricallyoutwards from the annular plate 40.

Thus, in the second embodiment of the present invention, when a numberof stator core assemblies 3 c′ are assembled to the core support plate4′, the number of first coupling protrusions 44′ are disposed betweenthe inner sides of the number of adjacent stator core assemblies 3 c′and the number of second coupling protrusions 45′ are disposed in across-shaped space S formed between the outer sides of the number ofadjacent stator core assemblies 3 c′. Finally, movement of the assembledstator core assemblies 3 c′ is restricted. Thus, the second embodimentis simpler than the first embodiment in view of the core support plate4′, and the former also more effectively support the number of statorcore assemblies 3 c′ than the latter.

As described above, an insertion groove 31′ is formed in the left andright sides between an outer extension 34′ of a division type statorcore 3 a′ and an outer flange 30 b of the bobbin 30 in the secondembodiment, so that a cross-shaped space S is formed between the outersides of the adjacent stator core assemblies 3 c′.

Since the remaining structure, the assembling process and the functionaleffect for the stator of the second embodiment are substantially same asthose of the first embodiment, the detailed description thereof will beomitted.

FIG. 14A is an exploded perspective view showing a relationship ofcoupling a stator core assembly and a core support plate according to athird embodiment of the present invention. FIG. 14B is an enlarged viewshowing a division type stator core.

Referring to FIGS. 14A and 14B, in the case of a stator according to athird embodiment of the present invention, a structure of a number ofstator core assemblies 3 c″ is similar to that of the second embodiment.However, coupling protrusions 30 c and 30 d whose cross-sections arecircular or rectangular are extended in the inner portion of the bobbin30 and the lower portions of the outer flanges 30 c and 30 b, guidegrooves 30 e-30 h for wiring and guiding coils 3 b (not shown) areformed, and coupling holes 47 c and 47 d corresponding to couplingprotrusions 30 c and 30 d are perforated on the bottom of an annularplate 40 instead of a number of first and second coupling protrusions44′ and 45′ so that a number of stator core assemblies 3 c″ areautomatically positioned and supported on an annular core support plate4″.

That is, the core support plate 4″ is formed by a press by using a BMC(Bulk Molding Compound) differently from the injection molded coresupport plates of the first and second embodiments. In order to fix thenumber of stator core assemblies 3 c″, inner and outer guide flanges 41and 42 are formed in the inner and outer circumferences of the annularplate 40, and simultaneously coupling holes 47 c and 47 d are perforatedon the bottom of the annular plate. Further, an extension 40 a where athroughhole 47 e through which a stator is fixed in a housing 2 of awashing machine is formed, is integrally formed in the innercircumference of the annular plate 40. When being combined in thehousing 2 of the washing machine, the extension 40 a plays a role ofblocking water leaking from the washing machine and flowing downwardsfrom penetrating into a motor.

Thus, in the stator of the third embodiment, coils are wound around thebobbin 30 where a core 3 a′ is combined to thereby prepare stator coreassemblies 3 c″, and then coupling protrusions 30 c and 30 d areinserted and fixed into coupling holes 47 c ad 47 d formed in the coresupport plate 4″. In this case, for example, a fixing structure betweenthe coupling protrusions 30 c and 30 d and the coupling holes 47 c and47 d, prevents a leading end from thermally being spliced and separatedafter being combined by a compulsive fitting or a hanging structure.

Thereafter, coils taken out from the stator core assemblies 3 c″ aremutually wired via the guide grooves 30 e-30 h, and a number of statorcore assemblies 3 c″ undergo an insert molding method usingthermosetting resin similarly to the first embodiment, to therebycontrive durability and waterproof.

As a result, in the third embodiment, the number of stator coreassemblies 3 c″ can be simply assembled with the core support plate 4″.In this case, since assembly positions in the radial and circumferentialdirections for the stator core assemblies 3 c″ are automaticallydetermined, an assembly productivity is very excellent.

Meanwhile, in the double rotor BLDC motor according to the presentinvention as shown in FIG. 9C, the rotor 5 is supported on the yokeframe 8 made of a pair of inner and outer yoke frames 8 a and 8 b inwhich the inner and outer rotors 5 a and 5 b where a number of magnets 6a and 6 b oppose each other also play a role of a yoke.

FIG. 16 is a cross-sectional view showing a support structure of doublerotors using a double yoke frame according to the present invention.Inner and outer yoke frames 8 a and 8 b in a yoke frame 8 are bent by apress, respectively. A first step structure 81 a is formed between thebent leading end of the inner yoke frame 8 a and the outer yoke frame 8b in which a magnet 6 a for an inner rotor 5 a is mounted. A second stepstructure 81 b where a magnet 6 b for an outer rotor 5 b is mounted, isformed in the leading end of the outer yoke frame 8 b. An annular groove82 in which part of the stator 3 can be inserted, is formed between thefirst and second step structures.

The number of magnets 6 a and 6 b are made of N-poles and S-poles whichare divided and magnetized, or divided pieces as shown in FIG. 1B. Also,a number of opposing magnets which are located in the opposing surfacesin the inner yoke 55 and the outer yoke 56 are disposed to have theopposing polarities, and simultaneously to have the opposing polaritieseven for the adjacent other magnets.

As shown in FIGS. 17A and 17B, the inner and outer yoke frames 8 a and 8b can be integrated into a variety of coupling structures “C”. That is,the inner and outer yoke frames can be coupled into one of a TOXcoupling structure shown in FIG. 17A, a TOX flat coupling structureshown in FIG. 17B, a spot welding coupling structure shown in FIG. 17C,and a riveting coupling structure shown in FIG. 17D.

The inner and outer yoke frames 8 a and 8 b are coupled with a bushing 7and supported to the rotational shaft 9. In this case, the bushing 7 arefabricated by sintering or forging as shown in FIGS. 18A and 18B, inwhich a number of coupling holes 71 are concentrically formed or anumber of coupling pins 72 for positioning and torque transferring arealternately protruded between the coupling holes 71, together with thenumber of coupling holes 71, in order to be combined with the contactingsurface of the inner yoke frame 8 a by a rivet or a bolt and nut Acoupling structure of a combination of a riveting 83 and a coupling pin72 is shown in FIG. 81C. In the case that the coupling structure isemployed, determination of a concentric position and transferring of arotational force are accomplished by the coupling pin 72, and a couplingbetween the bushing and the yoke frame is accomplished by a riveting ora bolt and nut combination.

Meanwhile, the rotor 5 can be fabricated into an integrated double rotorstructure as shown in FIGS. 19A and 19B, in addition to the double yokeframe structure.

The integrated double rotor structure 50 includes an inner rotor 50 awhere a number of N-poles and S-pole magnets 6 a are alternatelydisposed at the outer side of the annular inner yoke 51 a, and an outerrotor 50 b where a number of N-poles and S-pole magnets 6 b arealternately disposed at the outer side of the annular outer yoke 51 b.The inner and outer rotors 50 a and 50 b are integrally formed by aninsert molding method by using a BMC (Bulk Molding Compound) so that abushing 7 a combined with the rotational shaft 9 via a number of ribs 52which are extended in a radial pattern is supported in the center of theinner and outer rotors 50 a and 50 b. In this case, molding is performedat the portions other than the opposing surfaces of the magnets 6 a and6 b opposing each other in the inner and outer rotors 50 a and 50 b, andthe opposing magnets are disposed to have the mutually oppositepolarities.

Also, a number of cooling holes 10 for cooling stator coils insertedbetween the rotor supports 53 are formed in the rotor supports 53 madeof resin between the inner and outer rotors 50 a and 50 b, and a numberof cooling fan blades 54 are integrally formed on the lower surface ofthe outer rotor 50 b. Accordingly, air cooling for the stator isvoluntarily accomplished during rotation of the rotors.

As described above, the integrated double rotors 50 according to thepresent invention does not require a separate support plate since anumber of magnets 6 a and 6 b in the inner and outer rotors 50 a and 50b are integrated by using a BMC having a basic structural intensity.

Also, since a number of magnets 6 a and 6 b in the inner and outerrotors 50 a and 50 b are disposed concentrically by an insert moldingmethod, a fullness of a circle becomes high. Thus, when the rotors 50 aand 50 b are assembled with the stator 3, a magnetic gap can beuniformly maintained.

Also, since the rotors and the stator are integrated by using resin inthe above-described embodiments, the present invention has an effect ofproviding an excellent durability and water-proof performance. Thus, theBLDC motor according to the present invention is appropriate for a drumdriving source of a washing machine at a high humidity environment, butis not limited thereto. Also, a structure of mounting a stator can bevaried according to an apparatus where a motor is applied.

INDUSTRIAL APPLICABILITY

As described above, the BLDC motor according to the present inventioncan make the most of merits of a double rotor type which can increase amotor output and torque and remove demerits of a high material cost dueto a high performance magnet material by providing a motor at whichstator coils are completely divided. Also, the present invention makesthe most of merits having a small amount of axial vibration of a radialcore type motor and removes demerits of a high coil winding cost due touse of the integrated stator core and a high facility investment costdue to use of a dedicated winding machine.

The present invention can greatly enhance productivity of assembling astator by easily and mutually wiring coils by automatically positioningand fixing a plurality of stator core assemblies to a core support platewhen employing a double rotor and division type stator core structure.

Also, the present invention can enhance durability and reliability byintegrally molding the inner and outer rotors and bushings via an insertmolding method using thermosetting resin. Also, the double rotorstructure according to the present invention is appropriate for adriving source of a drum for a washing machine which requires waterproofand durability by integrally molding a stator via an insert moldingmethod using thermosetting resin and combining the stator together withthe integrated double rotors.

As described above, the present invention has been described withrespect to particularly preferred embodiments. However, the presentinvention is not limited to the above embodiments, and it is possiblefor one who has an ordinary skill in the art to make variousmodifications and variations, without departing off the spirit of thepresent invention.

1. An apparatus for driving a drum of a washing machine: a housing ofthe washing machine; a rotational shaft wherein its front portion isconnected to the drum and its intermediate portion is rotatably mountedin the housing; double rotors including an inner rotor and an outerrotor in which a central portion of the inner rotor and the outer rotoris combined with the rotational shaft via a bushing and is rotatablysupported, a plurality of N-pole and S-pole magnets are disposedalternately in annular form on different concentric circumferences ineach rotor, and opposing magnets with a predetermined distance betweenthe inner and outer rotors are disposed to have opposite polarities; andan annular stator which is installed with an air gap between the innerand outer rotors, wherein said stator is an integrated stator molded byusing thermosetting resin after each of a number of stator coreassemblies is obtained by which coil is wound on each of a number ofdivision type stator cores, and the number of the coil-wound stator coreassemblies are temporarily assembled.
 2. The driving apparatus of claim1, further comprising a number of cooling fan blades integrally formedon the lower surface of the outer rotor for air-cooling the statorduring rotation of the rotors.
 3. The driving apparatus of claim 1,wherein a magnetic circuit is formed through the inner and outer rotorsand the number of stator cores which are disposed between the inner andouter rotors with an air gap.
 4. The driving apparatus of claim 1,further comprising a Hall sensor located in an extension portion whichis extended in a central direction of the stator and is opposed to thelower end of the inner rotor, for generating a position signal detectingposition of the rotor rotating in order to control a current supply forthe coil.
 5. The driving apparatus of claim 1, wherein each of thenumber of division type stator cores is formed of “I” shape.
 6. Thedriving apparatus of claim 1, wherein the double rotors comprises: aninner rotor having an inner yoke formed into a cylindrical shape, and aplurality of first N-pole and S-pole magnets which are disposedalternately in annular form on the outer circumferential surface of theinner yoke; an outer rotor having an outer yoke having a relativelylarger diameter than that of the inner yoke so as to maintain apredetermined distance from the inner yoke, and a plurality of secondN-pole and S-pole magnets disposed alternately in annular form on theinner circumferential surface of the outer yoke, in which magnets facingthe plurality of the first N-pole and S-pole magnets are disposed tohave opposite polarities; and a rotor support which is integrated inannular form other than the opposing magnets in the inner and outerrotors, to simultaneously form a space where the stator is insertedbetween the inner and outer rotors, and is molded with thermosettingresin so that the inner end thereof is connected to the outercircumferential surface of the bushing.
 7. The driving apparatus ofclaim 5, further comprising a number of cooling holes formed in therotor support for cooling the coils inserted between the inner and outerrotors.
 8. The driving apparatus of claim 5, wherein a number of ribsare extended in a radial pattern between the bushing and the innerrotor, which are integrally formed with the inner and outer rotors. 9.The driving apparatus of claim 5, wherein the number of stator coreassemblies are temporarily assembled to an annular core support plate byan automatic positioning and supporting unit which automaticallypositions and supports the number of stator core assemblies to the coresupport plate with the predetermined interval.